In recent years, photographic light-sensitive materials have been required to attain various performances. It is well known to those skilled in the art that tabular grains are suitable for silver halide photographic emulsion in the light of sensitivity, graininess, sharpness and color sensitization efficiency. As tabular silver halide grains there are often used high silver bromide content tabular grains having twinning planes and {111} planes as main planes. However, there arises a problem that the rise in the amount of sensitizing dyes to be adsorbed to silver halide grains causes a rise in the inherent desensitization. On the other hand, it has been known that silver halide grains having {100} planes normally exhibit a good color sensitizability. Thus, it has been desired to develop tabular silver halide grains having {100} planes as main planes and provide these silver halide grains with a higher sensitivity.
For the details of high silver bromide content tabular silver halide grains having {100} planes as main planes, reference can be made to A. Mignot, E. Francois and M. Catinat, "Cristaux De Rbomure D'argent Plats, Limites Par Des Faces (100) Etnon Macles", Journal of Crystal Growth 123 (1974) pp. 207-213, JP-A-51-88017 (The term "JP-A" as used herein means an "unexamined published Japanese patent application"), and JP-B-64-8323 (The term "JP-B" as used herein means an "examined Japanese patent publication").
There is no end to the recent demand for simplification and expedition of development. There is also a growing demand for the reduction of the replenishment rate of processing solutions. These demands can advantageously be met by the use of high silver chloride content silver halide grains having a high solubility. For the details of high silver chloride content tabular grains having {100} planes as main planes, reference can be made to EP 0534395A1, and U.S. Pat. No. 5,264,337. However, high silver chloride content tabular silver halide grains are disadvantageous in that they contain twin grains in a high proportion and have a wide grain size distribution as shown in a grain photograph set forth in an example of EP 0534395A1.
On the other hand, it has heretofore been well known that silver halide grains are subjected to halogen conversion to attain a high sensitizability and control the pressure resistance of the grains. U.S. Pat. No. 2,592,250 discloses emulsion grains obtained by subjecting silver chloride grains to halogen conversion with bromide ions or iodide ions. JP-B-50-36978 discloses the use of an emulsion obtained by subjecting the surface of the foregoing emulsion to chemical sensitization. JP-A-61-122641 discloses an emulsion obtained by subjecting an emulsion containing chloride ions to halogen conversion with bromide ions or iodide ions in the presence of a solvent. JP-A-51-2417 discloses a silver halide grain growth method which comprises adding bromide ions or iodide ions to a silver chloride emulsion within 20 minutes after the production thereof so that it is subjected to physical ripening.
However, such a process for the preparation of emulsion grains cannot control the grain formation. As described in the above cited patent, the halogen conversion causes a total change in the size and crystal form of grains. Thus, such a scheme can hardly be applied to tabular grains.
JP-B-61-31454 discloses a method which comprises settling silver bromide on silver chloride grains by an accumulation method rather than by a halogen conversion method. Further, JP-A-63-305343 and JP-A-3-121442 disclose a method which comprises halogen conversion of the surface of grains with iodine to intensify the adsorption of dyes so that the site at which chemically-sensitized nuclei are formed can be con trolled by the site direction function of dyes.
However, these disclosures cannot be applied to high silver chloride content tabular grains having {100} planes as main planes.